Junior loud speaker



Dec. 15, 1925. 1,565,974

D. A. WHITSON JUNIOR LOUD SPEAKER Filed Nov, 20, 192:5 2 Sheets-Shut 1Z5 5 A '/7 ii/@TL 9/ 1/9 ZZ Z6 Z5' 5 /5 Z7 55 //0 90 5294 n l /05 79. 52/Z 94 v 1 57 4J 5 L A I2 ZI 5 57 55 Fig Z. 49 Z8 57 54 Z8 A l l d .I y//'ull- LJ jvafoe: 022W f4.- Vif/74775012,

ATTOENE YJ.

Dec D. A. WHITSON JUNIOR LOUD SPEAKER Filed Nov. 20, 1923 2 Sheets-Shut2 Patented Dec. 15, 1925.

UNITED STATES PATENT OFFICE.

DELMAR A. WHITSON, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO STENTORPHONECOMPANY, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF CALIFORNIA.

JUNIOR LOUD SPEAKER.

Application tiled November 20, 1923.

T 0 all whom t may concern:

Be it known that I, DELMAR A. WHrrsoN, a citizen of the United States,residing at Los Angeles, in the county of Los Angeles and State ofCalifornia, have invented a new and useful Junior Loud Speaker, of whichthe following is a specification.

This invention relates to loud speakers of the type commonly employedwith radio receiving sets, whereby a tone of sufficient magnitude to beheard throughout a fairly large sized room is produced.

In such devices itrris common practice to employ a diaphragm and meansfor vibrating the diaphragm, which vibrating means Ais actuated througha fluctuating audio current. Such vibrating means generally takes theform of the permanent magnet through which magnetic field it isproduced, this magnetic field having an armature therein which ispolarized b'y a fluctuating magnetic field produced by coils surroundingthe armature, these coils being energized through an exciting circuit. Agreat many elements or conditions enter into the efficient operation ofsuch devices. It is often found that where a device is designed andproportioned to operate on a certain strength of current with a fairdegree of perfection, such a device is inoperative on either a higher orlower voltage circuit.

It is an object of this invention to provide a loud speaker which willoperate over a Wide voltage range.

An element entering into the efficiency of a loud talker of thischaracter is the manner of mounting or supporting the armature. Certaindevices now in use which operate very successfully on low value currentselnploy delicate wires for supporting the armature and dependprincipally upon the stiffness of the diaphragm for restoration of thearmature after each vibratory movement due to magnetic action. It isfound that although this device operates very .successfully on a lowvoltage current, when the voltage is raised, the tone quality is lost,and distortion of tone values to the effect of producing a markedclatter results. In other types of devices the armature is snpportedupon a torsion plate which twists under the movement of the diaphragm,the

Serial No. 675,804.

torsion of the plate serving as a restorative force for returning thearmature after movement due to magnetic forces.

The high quality of tonal effects produced by my device may be creditedprincipally to the improved form of mounting employed for support of thearmature. This mounting consists of a plate having an edge to which thecentral portion of the armature is rigidly secured in such a manner thatthe movement of the armature produces a compound lexure in a designatedportion of the plate, this compound flexure consisting of a compositionof cantilever and beam fiexures which, judging from the effects producedby the use thereof, results in an evenly graduated restorative meanswhich approaches perfection in the design to the effect that high tonequality is obtainable over a wide range of-energy input, thus suitingthe device for use with various types to radio receiving equipment.

An object of the invention is to provide simplified forms ofconstruction for the various parts of the device whereby the loudspeaker may be produced and marketed at a comparatively low price.

. It is a further object of the invention to provide means for adjustingthe pole tixtures between the poles of the magnet, this adjustment beingpossible after assembly of the various motivating parts; and to providemeans for ad`usting the armature between the poles o the pole fixtures,thus enabling the adjustment of the armature in such a manner thatliability of freezing up is reduced to a minimum and enabling thefinding of the point of greatest sensltiveness.

The especial advantages of the invention and further objects thereofwill be made evident hereinafter.

Referring to the drawings which are for illustrative purposes only,

Fig. 1 is a horizontal section through a loud speaker embodying thefeatures of my invention.

Fig. 2 is a section taken on a plane represented by the line 2 2 of Fig.1.

Fig. 3 is an enlarged fragmentary section as indicated by the line 3-3of Fig. 1.

Fig. t is a fragmentary section taken on a plane represented by the line4.-4 of Fie'. JS showing the pole piece fixture and the field and thefield coils in place therein.

Fig. 5 is an enlarged perspective View of a pole piece fixture.

Fig. 6 is an enlarged sectional perspective view taken on a planeindicated by the line ('if--G of Fig` 4- and showing the constructionolthe mounting plate and the manner in which the armature is securedthereto.

Fig. 7 is an enlarged Afragmentary section showingr the novel meansemployed t'or securing the primary and secondary plates together. v

Fig. 8 shows the manner in which leads are connected into the device.

Fig. S) is a perspective View of the magnet clamping yoke.

Fig. 10 is a diagram illustrating the action produced in the device.

As shown principally in Fig. 1 of the drawing, a circular stampedprimary plate is formed with a central opening defined by an outwardprojecting lip 16, in which is secured a threaded cup-shaped member 17having the bottoni l8- thereof perforated as indicated at 19. The member15 is ste )pcd so as to provide an annular edgewardly disposedledge 2lagainst which the circular edge of a diaphragm 22 is placed. Theedge ofthe .diaphraglni 22 is gripped by a ring 23 preferably ol rubber orother resilient material, this ring being forced against the ledge 2l bya secopdary plate 24 which is dish-shaped as indicated at 25 and isprovided with an upwardly turned lip 26. The manner in which the plate2t is secured in place is of marked simplicity and novelty, consistingof three clips 28 spaced at angles of substantially l2() degrees, theseclips having the. outer ends 2S) thereof turned downwardly.' asindicated in Fig. 7. The central portions 2l() of the clips 2S rest onthe annular corner 3l of the secondary plate 24 and serve as levers forforcing the plate 24 inwardly. This leverage action is accomplished asfollows:

The downwardly turned end 29 of each clip 28 engages the interior of theinwardly rolled semi-circular lip 33 of the primary plate. 15. lVhenscrews 254, which thread into holes provided in the member 24 and whichextend through holes in .the inner ends ot' the clips 28, are tighteneddown the ends 29 react against the inner faces of the lips fill iii thedirection indicated by the arrow 35. thus causing pressure to be appliedat the corners 3l by the central portion ol' the clip in such a mannerthat the plate 2l is forced tightly against the rin 23. 'lhis method ofseeurenient is very rigit and is accomplished without screws or othersecuring means showing upon the face of the Iprimary plate 15.

The secondary plate 24 serves as a mounting for a permanent horseshoe orU-shaped magnet 37, which is secured thereto by a special form of yoke38 ol the design shown in Fig. 9. This yoke has a central base portion39, from the ends of which there outwardly extend legs 40 havinglaterally projecting ends'41. From one side of the base portion 39 thereupwardly extends a leg 42, which segregates into a center post 43 havinga laterally extending end 44 provided with a threaded hole 45, andbinding ost supports 46 and 4-7 which are in the erm of tongues havingholes 48 drilled in the ends thereof. As shown in Figs. 1 and 2, thelegs 40 of the yoke rest snugly Within the poles 4D and 50 of the magnet37 and the ends 41 engage the outer faces of the poles with siiflicientpressure to hold the magnet tightly against the member 24 When thescrews 52 are screwed tightly down. A semi-circularanotch 53 is formedin the base portion fit) so that the central opening 54- of the member24 will not be obstructed.

Secured on the inner face of each pole 4) a'nd 5() is a fixture 56formed from mild steel or iron in the manner shown in Fig. 5. flhesefixtures 5G are counterparts and when in use are placed in invertedpositions, as ,shown clearly in Fig. 3. The fixture 56 comprises a baseIor attachment portion 5T, from which there outwardly extends fromopposing edges 5!) a pair ot' legs 58. From one transverse edge 6() ot'the Ybase portion 57 there is outwardly lient a web portion 62 whichextends between the inner faces of the legs 58, and projecting from the'other y transverse edge 63 is a lug (54 turned so as to lie in a planeparallel with the legs 58 and having a threaded hole (35 therein. Thelegs 5S are ofl'set in the manner shown at 6T so that the pole faces 68thereof lie in a plane intermediate the edges 6l) and (53, which planeis perpendicular to the plane of the inner faces ot' the legs 58. i'

As sho-wn in Fig. Il, the fixtures o6 are placed in inverted position sothat the pole faces (3S of one fisture will lie adjacent and parallel tothe pole faces ol the other fixtures, the fixtures being held in placeby screws 70 which extend through the magnet poles 4f) and 5() andthread into the base portion 5T of the fixtures 56. The fixtures asshown are turned sideways with respect to the poles so that the fares(38 thereof will lie parallel to a plane designated by the line 4 4 ofFig. 5l, which plane when the iiiagnet is secured to the secondary plate2l is parallel to the surface ot' the plate 24. lVlien the fixtures 56are placed in this manner. the lugs 64 lie substantially in a centralplane and serve as securing points for an armature mounting plate 73.

The armature mounting plate should receive especial consideration astherein lies a principal feature of the device and constitutes a partwhich is particularly important to the etlicient operation thereof. Thisplate as shown in Figs. 3, 4 and 6 is preferably of rectangular formwith diagonally extending ears 74 having holes 7 5`therein. The mountingplate is preferably stamped from bronze and has a continuous oblongchannel 7 6 depressed therein, which channel has a rigid frame for thecentral flexure portion 77 of the mounting plate which has an elongatedrectangular opening 78 therein through Which'an armature 79 extends,this armature preferably consisting of a flat bar of soft iron andhaving a lever arm 81 extending from one end thereof. Although, it isconvenient to confine a central iiexure portion 77 of the plate b aframe composed of a depressed channel 46, it Will be recognized thatother frame means may be employed to rgidly support the flexure ortion77. The armature 79 is secured rigidly to the upper edge 83 presented bythe tlexure portion, this being accomplished by the use of a U-sliapedwire member 84, the legs 85 of which extend through holes in thearmature and rest against the face of the flexure portion 77, silversolder being flowed into the corner between the armature 79 and over thelegs 85, thus rigidly securing the armature to the flexure section 77 insuch a. manner that any movement of the ends of the armature will resultin a compound fiexui'e in the portion 77. This compound flexure consistsof a cantilever flexure, of that portion 77 of the plate to which thearmature is secured, along the lineA-A and a beam fiexure along the lineB-B. The reason that the restorative action of this compound flexure rofthe supporting platel should be more eliticient than a torsionalrestoration as accomplished by Edgerton or a simple iiexure as attainedby Baldwin, is not theoretically accounted for; but numerous experimentsdefinitely prove that the construction herein described is essential inthe attainment of the elicient results, and in comparative tests, thequality and magnitude of tone delivered is plainly superior to theresults attained in the use of the devices now on the market. It isfound also that the enclosing of the central flexure area by a frame forvmaintaining the peripheral edges of the area rigid contributes to theresults attained.

The mounting plate 73 is disposed intermediately between the legs 58 ofthe fixtures 56 as shown, and is supported by screws 87 which extendthrough the openings 75 and thread into the lugs 64. The openings 75 areof larger diameter than the screws 87, thus allowing a relative movementof the plate so that the armature may be readily centralized between thepole faces of the legs 58 as shown in Figs. 1 and 3. The projection 81of the armature 79 extends in# Wardly between the poles 49 and 50 of thepermanent magnet and the movement thereof is linked with the diaphragm22 by a small rod which extends through the opening 54 in the mountingplate 24. It will be noticed that the lugs 64 project slightly beyondthe side faces of the permanent magnet 37 and that when the magnet issecured against the plate 24, the uppermost lug G4 is received in anopening 91 stamped in the' plate 24 as shown in Fig. 1.

A simplified form of exciting coil construction is employed in thedevice, this construction consisting of a pair of rectangular end plates94 between which the winding is held. This construction employs nointerior sleeve for supporting the Winding and the end plates 94, thecoil being Wound between the lates 94 on a mandrel of rectangularsection, the winding being impregnated with liquid Celluloid so that theseparate turns of the wire are cemented together and to the inner facesof the plates 94. The coils 92 are of such rectangular forni that theyfit snugly between the base portions 57 of the fixtures 56 when theselixtures are secured between the poles 49 and 50 of the permanentmagnet, the openings through the coils formed by the mandrel upon whichthey are wound, providing ample clearance for the armature to swingtherein. The form of pole fixtures employed in this device provides aboxed-in space which receives the coils, thus forming a very compact andeasily assembled mechanism.

Means for connecting into the energizing circuit are provided in theform of pins 95 which extend through bushings 96 set in the openings 48of the tongue members 47 stamped on the yoke 39. This pin is threaded atone end so as to receive a nut 97 and has an eye 98 in the opposite endthereof. The leads 100 and 101 from the coils 92 are soldered to the endof the pin 95 as shown. The external conductors are led through anopening 102 in the cup shaped cover 103, and the ends thereof insertedthrough the eyes 98, whereupon the nuts 97 are tightened so as to drawthe pin inwardly through the bushing in a manner to grip the conductorstightly. This simple form of connection eliminates considerable time inthe assembly of the device and the parts thereof are inexpensive. Thecup member 103 which serves as a cover for the mechanism is secured by asingle screw 105, Fig. 1, which threads into the threaded hole 45 of themounting post 43. The rim of the cup rests within the lip 33 of theprimary plate 15 and against the clips 28 as shown. This constructionprovides an easy access to the interior mechanism and enables the deviceto be accurately adjusted before placing on the cover.

I claim as my invention:

iso

1. In a loud speaker, the combination of means for producing a pair ofuni-directional parallel magnetic fields; an armature extending betweensaid magnetic fields and with the ends thereof in said magnetic fields;means for polarizing said armature; a diaphragm; means for transmittingthe movement of said armature to said diaphragm; and a sup orting platehaving a flexure area confined, by a frame structure, said armaturebeing attached rigidly to the edge of said plate iii such a manner thatthe movement of said armature is resisted by compound flexure iu saidplate.

2. In a loud speaker, the combination of means for producing a pairof-uni-directional aral-lel magnetic fields; an armature extendingbetween said magnetic fields and with the ends thereof iu said magneticields; means for polarizing said armature;

a. diaphragm;.means for transmitting the movement ofb said armature tosaid diaphragm; and a supporting plate, said plate having a flexure areaconfined by a frame structure, and said arn'iature being attachedrigidly to the edge of said plate in such a manner that the movement ofsaid arniaiure is resisted by compound tlexure in the flexure area ofsaid plate.

3. In a loud speaker, the eonibination of: means for producing a pair ofunidirec tional parallel magnetic fields; au armature. extending betweensaid magnetic fields and with the ends thereof in said magnetic fields;means for polarizing said armatlire; a diaphragm; means for transmittingthe movement of said armature to said diaphragm; and a supporting plate,said plate having a centrally disposed flexurc area confined by a framestructure and provided with an elongated opening through which saidarmature extends, said armature being rigidly secured to onelongitudinal edge of said opening so that the movement of said armatureis resisted by compound fiexure in the flexure area of said plate.

4. In a loud speaker, the combination of: means for producing a pair ofuni-directional arallel magnetic fields; an armature extending betweensaid magnetic fields and with' the ends thereof in said magnetic fields;means for polarizing said armature; a diaphragm; means for transmittingthe movement of said armature to said diaphragm; and a supporting plate,said plate having a centrally dispod fiexure area confined by a framestructure and provided with an elongated opening through which saidarmature extends, said armature being rigidly secured to onelongitudinal edge of said opening so that the movement of said armatureis resisted by compound flexurc in the flexure area of said plate.

5. In a loud s eaker, the combination of: means for pro ucing a pair ofuni-directional parallel magnetic fields; an armature extending betweensaid magnetic fields and with the ends thereof in saidv magnetic fields;means for polarizing said armature; a diaphragm; means for transmittingthe movement of said armature to said diaphragm; and a supporting plate,said plate having a centrally disposed fiexure area rouined by a framestructure consisting of a continuous channel depressed in said plate andprovided with an elongated opening through which said armature extends,said armature being rigidly secured to one longitudinal edge of saidopening so that the movement of said armature is resisted by compoundtiexure in the iexure area of said plate.

6. In a loud speaker, the combination of: means for producing a pair ofuni-directional paral el magnetic fields; an armature extending betweensaid magnetic iields and with the ends thereof in said magnetic fields:eoils surrounding said armature lor creating an excited lield polarizingsaid armature; circuit leads to said coils; a diapliragm; means fortransmitting the movement of said armature to said diaphragm; and asuppoi ting plate having a tlexure area confined by a vframe structure,said armature being attached rigidly to an edge of the tiexure area ofsaid plate in such a manner that the movement of said armature isresisted by compound fiexnrc in said plant.

7. In a loud speaker, the combination ol': means for producing a air ofuni-directional parallel magnetic elds; an armature extending betweensaid magnetic fields and with the ends thereof in said magnetic fields;coils surrounding said armature for creating an excited field polarizingsaid armature; circuit leads to said coils; a diaphragm; means fortransmitting the movement of said armature to said diaphragm; and asupporting plate dis )osed centrally with respect to the ends o saidarmature, said plate having a centrally disposed iexure area confined bya Vframe structure consisting of a continuous channel depressed in saidplate and provided with an elongated opening through which said armatureextends, said armature being rigidly secured to one longitudinal edge ofsaid opening so that the movement of said armature is resisted bycompound flexure in the flexure area of said plate.

8. In a loud speaker, the combination of: a permanent U-shaped magnet; apair of fixtures on said magnet for dividing the How of magnetic fluxinto a pair of uni-directional parallel magnetic fields; an armatureextending between said magnetic fields and with the ends thereof in saidmagnetic fields; means for polarizing said armature; a diaphragm; meansfor transmitting the movement of said armature to said diaphragm; and asupporting plate disposed centrally with respect to the ends of saidarmature, and having a flexure area confined by a frame structure, saidarmature being attached rigidly to an edge of the fiexure area of saidplate in such a manner that the movement of said armature is resisted bycompound fiexure in said plate.

9. In a loud speaker, the combination of: a permanent U-shaped magnet; aair of fixtures on said magnet for dividing the flow of magnetic fluxinto a pair of unidirectional parallel magnetic fields; an armatureextending between said magnetic fields and with the ends thereof in saidmagnetic fields; coils surrounding said armature for creating an excitedfield polarizing said armature; circuit leads to said coils; adiaphragm; means for transmitting the movement of said armature to saiddiaphragln; and a supporting plate disposed centrally with respect tothe ends of said armature, said plate having a centrally disposedfiexure area confined by a frame structure consisting of a continuouschannel depressed in said plate and provided with an elongated openingthrough which said armature extends, said armature being rigidly securedto one longitudinal edge of said opening so that the movement of saidamature is resisted by compound fiexure in the fiexure area of saidplate.

10. In a loud speaker, the combination of: a permanent 'U-shaped magnet;a fixture on each arm of said magnet, each of said fixtures having apair of parallel arms, the

' arms of each fixture extending in position spaced apart from the armsof the other fixture in a manner to divide the flow of4 flux of saidmagnet in a pair of uni-directional fields; an armature having therespective ends thereof in said fields; a plate for supporting saidarmature, said plate having la flexure area confined .by a framestructure and having an opening thereln through which said armatureextends; and means for adjustably securing said plate in such a mannerthat said armature may be adjusted in position relative to said fixturearms by movement of said plate.

11. In a loud speaker, the combination of a permanent 'U-shaped magnet;a fixture on each arm of said magnet, each of said fixtures having apair of parallel arms, the arms of each fixture extending in position saced apart from the arms of the other xture in a manner to divide theflow of flux of said magnet in a pair of uni-directional fields; anarmature having the respective ends thereof in said fields; a plate forsupporting said armature, said plate having a flexure area confined by aframe structure and having an opening therein through which saidarmature extends; and lugs on said fixtures to which said plate is'adjustably secured in such a manner that said armature may be adjustedin position relative to said fixture arms by movement of said plate.

12. In a loud speaker, the combinationof: a permanent U-shaped magnet; afixture on each arm of said magnet, each of. said fixtures consisting ofa base p0rtion having a` pair of arms extending outwardl from one Sidethereof; the arms of each xture overlapping the arms of the otherfixture in spaced relationship in a manner to divide the fioW of flux ofsaid magnet in a pair of uni-directional fields; an armature having therespective ends thereof 1n said fields; a plate for supporting saidarmature said plate having a fiexure area confined by a frame structureand having an opening in said fiexure area through which said armatureextends; and means for adjustably securing said plate in such a mannerthat said armature may be adjusted in position relative to said fixturearms bv movement of said plate.

13. In a loud speaker, the combination of: a permanent U-shaped magnet;a fixture on each arm of said magnet, each of said fixtures consistingof a base portion having a pair of arms extending outwardly from oneside thereof; the arms of each fixture overlapping the arms of the otherfixture in spaced relationshi having a pair of parallel arms, the arms oeach fixture extending in position spaced apart from the arms of theother fixture in a manner to divide the flow of flux of said magnet in apair of uni-directional fields; an armature having the respective endsthereof in said fields; a plate for supporting said armature, said platehaving a flexure area confined b a frame structure and having an opening1n said fiexure area through which said armature extends; and lugs onsaid fixtures to which said plate is adjustably secured in such a mannerthat said armature may be adjusted in position relative to said fixturearms by movement of said plate.

14. In a loud speaker, the combination of: a primary plate having acentral opening and means for attachment of an amplifier, said primaryplate having an inwardly turned lip formed around the edge thereof; adiaphragm resting against the rearward face of said primary plate; asecondary plate covering said diaphragm; and clips arranged around theedge of said secondaryplate and engaging under said li on said primaryplate in a manner to orce said secondary plate against said diaphragm.

15. In a loud speaker, the combination of: a primary plate having acentral opening and means for attachment of an amplifier, said (primaryplate having an inwardly turne` lip formed around the edge thereof; adiaphragm resting against the rearward fare of said primary plate; asecondary plate eovering said diaphragm; and clips arranged around theedge of said secondary plate and engaging under said li on said primaryplate in a manner to oree said secondary plate against said diaphragm; amagnet; a yoke for holding said magnet against said secondary plate;means associated with said magnet for vibrating said diaphragm; a cuppedcover member for said magnet, held in place by a screw threaded intosaid yoke.

16. In telephonie apparatus: a plate for supporting an armature, saidplate having a exure area confined by a frame strueture.

17. In telephonie apparatus: a plate for supporting an armature, saidplate having a lexure area confined by a frame structure consisting ot'a continuous channel depressed in said plate.

18. In telephonie apparatus: a plate for supporting an armature, saidplate having a tlexure area confined by a frame structure, and anelongated slot in said fleXure area adapted to reeeive the armature.

1S). In telephonie apparatus: a plate for supporting an armature, saidplate having a lexure area confined by a frame structure rousisting of acontinuous channel depressed in said plate, and an elongated slot 1nsaid ilexure area.

20. In telephonie apparatus: a plate for supporting an armature, saidplate having a llexure area. eonlined by a frame structure Vronsistingof a continuous channel depressed in said plate, said plate having anelongated slot in said flexure area; and an armature in said slottransverse to said plate.

2l. In telephonie apparatus: a plate for supporting an aruntture, saidplate having a tiexure area eon fined by a frame structure and having anelongated slot in said lexure area; and an armature in said slottransverse to said plate.

22. In telephonie apparatus: a plate for supporting an armature, saidplate having a lexure area eontined by a frame structure and having anelongated slot in said fiexure area; an armature in said slot transverseto said plate; and a diaphragm responsive to the movements of saidarmature.

28. In telephonie apparatus: a plate for supporting an armature, saidplate having a. flexure area eonfined by a frame structure and having anelongated slot in said flexure area; an armature in said slot transverseto said plate; a diaphragm, and means eonneeting one end of saidarmature to said diaphragm.

24. In telephonie apparatus: a plate for supporting an armature, saidplate having a flexure area eonlined by a frame structure and having anelongated slot in said lexnre area; an armature in said slot transverseto said plate; a diaphragm; and means rou.- neeting one end of saidarmature to said diaphragm, the other end of said armature being free.

25. In telephonie apparatus: a plate for supporting an armature, saidplate having a tlexure area confined by a frame structure and having anelongated slot in said flexure area;an ax'mature in said slot transverseto said plate; a diaphragm responsive to the movements of said armature;a. primary plate on one side of said diaphragm, said primary platehaving an inwardly turned lip formed around the edge thereof; a secondary plate on the other side of said diaphragm from said primary late;and clips arranged around the edge o said secondary plate and engagingunder said li on said primary plate in a manner to oree said secondaryplate against said diaphragm.

26. In telephonie apparatus: a late for supporting an armature, saidplate aving a flexure area confined by a. frame structure and having anelongated slot in said fiexure area; an armature in said slot transverseto said plate; a diaphragm responsive to the movements of said armature;a primary plate on one side of said diaphragm, said primary plate havingan inwardly turned lip formed around the edge thereof; a secondary plateon the other side of said diaphragm from said primary plate; clipsarranged around the edge of said secondary plate and engaging under saidli on said primary plate in a manner to oree said secondary plateagainst said diaphragm; and means for attaching an amplifier to saidprimary plate.

27. In telephonie apparatus: a plate for supporting an armature, saidplate having a flexure area confined by a frame structure and having anelongated slot in said iiexure area; and an armature in said slottransverse to said late, said armature being secured to the exure areaof said plate.

28. In a loud speaker, the combination of: a primary plate having acentral opening, said primary plate having an inwardlfy turned lipformed around the edge thereo a diaphragm resting against the rearwardfare of said primary plate; a secondary plate eovering said diaphragm;and slips arranged around the edge of said secondary plate and engagingunder said li on said primary plate in a manner to iihree Said secondaryplate against said diaphragm.

29. In a loud speaker, the combination of: a primary plate having acentral opening, said primary plate having an inwardly turned lip formedaround the edge thereof; a diaphragm resting against the rearward faceof said primary plate; a secondary plate covering said diaphragm; elipsarranged around the edge of said secondary plate and engaging under saidli 3 on said primary plate in a manner to orce said secondary plateagainst said dia hragm; a magnet; a yoke orholding sa1d magnet againstsaid secondary plate; means associated with said magnet for vibratingsaid dia hragm; and a cupped cover member for sai magnet, held 1n placeby a screw threaded into said yoke.

-In testimony whereof, I have hereunto Set my hand at Los Angeles,California, this '13th day of November, 1923.

DELMAR A. WHITSON.

ranged around the edge of said secondary plate and engaging under saidlip on said primary plate in a manner to force said secondary plateagainst said diaphragm; a magnet; a yoke for holding said magnet againstsaid secondary plate; means associated with said magnet for vibratingsaid diaphragm; and a clipped oever member for said magnet, held inplace by a screw threaded into said yoke.

In testimony whereof, I have hereunto set my hand at Los Angeles,California, this 13th day of November, 1923.

DELMAR A. VVHITSON.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,565,974, grantedDecember l5, 1925, upon the application of Delmar A. Whtson, of LosAngeles, California, for an improvement m Junior Loud Speakers, errorsappear in the printed specification re uring correction as follows: Page4, line 98, claim 6, for the word plant read p ate; page 6, line 58,claim 23, after the word diaphragm strike out the comma. and insert asemicolon, and line 117, claim 28, for the word slips read clips; andthat the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Ollice.

Signed and sealed this 19th day of January, A. D. 1926.

[SEAL] WM. A. KINNAN,

Acting Commissioner of Patents.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,565,974, grantedDecember 15, 1925, upon the application of Delmar A. Whitson, of LosAngeles, California, for an improvement 1n Junior Loud gpeakers, errorsappear in the printed specification re uiring correction as follows:Page 4, line 98, claim 6, for the word plant read p e; page 6, line 58,claim 23, after the word diaphragm strike out the comma and insert asemicolon, and line 117, claim 28, for the word slips rend dips; andthat the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 19th day of January, A. D. 1926.

[BEAM] WM. A. KINNAN,

Acting Uommz'ssz'omr of Patents.

